The Kretschmar Hall Observatory

Fall 2022: Events

With the vibration damping improvement from the tuned mass damper and the clear skies provided by a late summer drought, this has been our best quarter for viewing ever. Jupiter was at its closest approach in decades and Saturn was also in a prime viewing location. We got in the following groups before the fall rains started and put an end to the clear weather:

September 15, Faculty and staff. M13, Jupiter, and Saturn.
October 1, Students in Conceptual Physics, General Physics, and Principles of Physics. Jupiter, Saturn, M13, M31, and the moon.
October 12, All of WWU as announced in the 11am daily email. Again Jupiter, Saturn, M13, M31, and the moon.
October 22, Parents Weekend. Jupiter, Saturn, and M13. The clouds came up during the viewing so the season is over now.

Summer 2022: Vibration Damping

The air legs beneath the telescope reduce the vibration by about 50% but also introduce a drift that is telescope angle dependent. As a result, moving the telescope to a new location always includes steps of fine position correction. This makes the telescope harder to use with large groups of people who want to look at different objects.

The position of a distant object is shown in the graph at left. The blue line shows the undamped position jiggling about in both axes. The yellow line shows the air legs reducing the jiggle but introducing a vertical drift that is almost double the jiggle.

The work this summer focused on trying to get another method of vibration suppression that was as good as the air legs. At the end of the summer, the air legs were removed from the system and a tuned mass damper (TMD) was added. As shown in the picture, the TMD is mounted near the top of the pier and is made of 6 lead bricks floating on sorbothane. The major vibration peaks at 6 and 10 Hz have a reduction of about 5 dB in each axis.

Spring 2022: Vibration Damping and Events

Over Christmas break, a better damping solution than inner tubes was put into place. A vibration damping company, TMC, makes air legs so four of those were put between the telescope and the pier as shown in the picture at right. They reduce down the vibration quite a bit.

May 2022: Observation with the Physics Majors, the General Physics class, Principles of Physics class, and Conceptual Physics class. All the planets rose about 2am so we looked instead at M31 and the moon.

Fall 2021: Vibrational Testing and Events

Over the summer and into the fall, the vibration on the telescope pier was studied using a combination of accelerometers and the camera. The data shown in the picture at left was taken on the eyepiece of the telescope. While there are vibration at higher frequencies, the double peaks at 6 and 9 Hz appear to be the largest ones.

November 2021: Observation was done with the General Physics class and the physics majors in spite of the vibration on the telescope. We had good viewing of the moon, Jupiter, and Saturn.

The first step on vibration suppression was to float the telescope on inner tubes. A special vibration material called sorbothane was also tried. These methods helped a bit but were not enough to be the final solution.

Spring 2021: Events

April 2021: We celebrated the return to campus after the COVID lockdown with an observation evening for the General Physics class and all physics majors. The 16" telescope was used primarily to view the full moon. The portable telescopes on the observation deck were used to view Mars. A number of students used cell phones to capture pictures through the telescopes.

After the viewing in April, a new telescope camera was purchased. The previous camera was about 20 years old, connected to a computer using a parallel part, and was water-cooled. This new camera is USB 3.0 and is air cooled so it is much easier to use. The magnification on the camera is designed for planetary distances. The images on the banner at the top of this page were taken with the new camera.

Before the camera was purchased, vibration was visible in the images seen on the telescope but was difficult to measure. With the camera, the vibration was quantified and a project improvement plan was started.

Observatory History

An observatory was planned for the top of the third floor when Kretschmar Hall was built in 1962. However, since the third floor was not built at that time, neither was the observatory. When a third floor was finally added, it provided an opportunity to complete add this feature.

The observatory is situated on the roof of Kretschmar Hall and is accessible via stair from the third floor of Kretschmar Hall and via elevator from Chan Shun Pavilion. It is currently equipped with a 16" Schmidt-Cassegrain telescope and an external observation deck for use by smaller telescopes.